Gelatin has long been used as a dispersion medium of silver halide grains in a silver halide emulsion. In the conventional silver salt photographic system, gelatin plays an important role over the entire process from silver halide grain growth to protection of the final photographic images.
When gelatin is classified by its molecular weight, it is classified into a high molecular weight gelatin with a molecular weight of 300,000 or more, a .gamma. component with a molecular weight of around 300,000, a .beta. component with a molecular weight of around 200,000, .alpha. a component with a molecular weight of around 100,000, and a low molecular weight gelatin with a molecular weight of 100,000 or less. The molecular weight distribution varies depending upon the raw material or the manufacturing conditions of solubilizing treatment, and upon the extraction condition.
As gelatin for photographic use, a mixture of these gelatins with various molecular weights is used, and generally, gelatin with an average molecular weight of 70,000 to 130,00 is preferably used, which is obtained by lime-treating hide gelatin or ossein gelatin.
It is well-known that gelatin as a dispersion medium has an influence on silver halide grain crystal formation or growth in the formation process of the silver halide grains. Herein, the molecular weight or structure of gelatin or impurities contained in the gelatin are considered to influence in this process.
In Japanese Patent O.P.I. Publication Nos. 1-158426, 1-213637 and 2-838 is disclosed a technique which increases a content of tabular silver halide grains or hexagonal tabular silver halide grains by employing low molecular weight gelatin as a dispersion medium in the manufacture of silver halide emulsions. The monodisperse emulsion having such a silver halide shape and a uniform grain size distribution is considered to be effective in obtaining a silver halide photographic light sensitive material providing both high sensitivity and high image quality. However, when the low molecular weight gelatin is used in the silver halide emulsion manufacturing process, there is the problem in that storage stability of the silver halide emulsion is deteriorated.